Re: [PATCH] bpf: Try harder when allocating memory for maps

[Michal Hocko <mhocko@kernel.org>]

On Fri 08-03-19 12:14:16, Martynas Pumputis wrote:
> 
> 
> On 3/8/19 9:44 AM, Michal Hocko wrote:
> > On Fri 08-03-19 09:08:57, Martynas Pumputis wrote:
> > > It has been observed that sometimes memory allocation for BPF maps
> > > fails when there is no obvious memory pressure in a system.
> > > 
> > > E.g. the map (BPF_MAP_TYPE_LRU_HASH, key=38, value=56, max_elems=524288)
> > > could not be created due to due to vmalloc unable to allocate 75497472B,
> > > when the system's memory consumption (in MB) was the following:
> > > 
> > >      Total: 3942 Used: 837 (21.24%) Free: 138 Buffers: 239 Cached: 2727
> > 
> > Hmm 75MB is quite large and much larger than the slab/page allocator
> > cann provide so this is not really a fragmentation issue. Vmalloc does
> > respect noretry but considering that there shouldn't be a large memory
> > pressure I wonder how NORETRY managed to fail the allocation. Do you
> > happen to have the allocation failure report?
> 
> I got /proc/{meminfo,vmstat,vmallocinfo} just after the allocation has
> failed:
> https://gist.github.com/brb/62092c1d83daa6527271b88f0352e32d

dmesg with the allocation failure report would be more helpful

Thanks!
-- 
Michal Hocko
SUSE Labs